Food prices already stand at record levels, according to the Food and Agriculture Organization of the United Nations. Unfavorable weather has hurt grain production, and some countries have started building their strategic reserves through hoarding. At the same time, rising incomes in China and other fast-developing countries have boosted demand for livestock feed.

Among the world's poorest citizens, the food crisis isn't a looming threat. It's a reality. Complaints about the high cost of bread and other basics led directly to the public protests in Tunisia that toppled its authoritarian regime. Inspired by the Tunisian example, Egyptians then took to the streets, and now Libyans are in revolt, shaking confidence in the stability of ruling powers across the Middle East.

The American Midwest could be ground zero for the next political shockwave. With grain stockpiles at such alarmingly low levels, U.S. farmers will plant fence row-to-fence row this spring. But even a bumper crop won't be enough to fill all the world's empty bins. And the Farm Belt may not deliver: Our last major drought struck in 1988. Some forecasters consider another one overdue.

Given the precarious balance between supply and demand, any significant crop failure would force immediate changes in U.S. ethanol policy. In the coming year, absent any reform, 5 billion bushels of corn will go into ethanol — more than double the amount we've slated for export to hungry customers abroad. If prices skyrocket and food riots break out in impoverished parts of the world, it's hard to imagine Americans putting all that corn into their gas tanks.

Yet shifting grain back into the food supply during an emergency would create problems that need to be planned for today. As it is, replacing almost 14 billion gallons of ethanol on short notice would drive up prices at the pump by as much as $1.40 per gallon, according to Dan Basse, a market analyst in Chicago.

We can't afford to wait for that economic accident to happen. For starters, we need to lift protectionist tariffs that subsidize the domestic corn-ethanol industry by keeping out biofuel brewed elsewhere. We need to reduce our economy-distorting subsidies and mandates for corn-based fuel as well, to limit ethanol's growing claim on our corn supply. On Thursday, former President Bill Clinton voiced a good idea for periodically re-assessing government support of the industry based on food availability.

The Congressional Budget Office estimated that in 2007 and 2008, ethanol alone accounted for at least 10 percent of the rise in domestic food prices.

Confronted in recent weeks over the impact of its product on the stability of the Middle East, the ethanol industry issued a comically implausible denial. Ethanol affecting food prices? Impossible!

What nonsense. If its trade group put its money behind that claim at the Chicago Board of Trade, it would be out of business in a matter of minutes. We need to wean our nation from its overdependence on corn-brewed fuel. Act now, or millions could go hungry later.